Oxytocin Reduces Intravesical Pressure in Anesthetized Female Rats: Action on Oxytocin Receptors of the Urinary Bladder.

Eduardo M Cafarchio,Rui M B Maciel,Laura B M Maifrino,Gisele Giannocco,Itatiana F Rodart,Patrik Aronsson,Monica A Sato,Daniel P Venancio,Luiz A Da Silva,Janaina S De Souza,Luciana C Auresco,Bruno B Antonio

doi:10.3389/fphys.2020.00382

Abstract

Urinary bladder dysfunction affects several people worldwide and shows higher prevalence in women. Micturition is dependent on the Barrington’s nucleus, pontine urine storage center and periaqueductal gray matter, but other brain stem areas are involved in the bladder regulation. Neurons in the medulla oblongata send projections to hypothalamic nuclei as the supraoptic nucleus, which synthetizes oxytocin and in its turn, this peptide is released in the circulation. We investigated the effects of intravenous injection of oxytocin (OT) on the urinary bladder in sham and ovariectomized rats. We also evaluated the topical (in situ) action of OT on intravesical pressure (IP) as well as the existence of oxytocin receptors in the urinary bladder. In sham female Wistar rats, anesthetized with isoflurane, intravenous infusion of OT (10 ng/kg) significantly decreased the IP (–47.5 ± 1.2%) compared to saline (3.4 ± 0.7%). Similar effect in IP was observed in ovariectomized rats after i.v. OT (–41.9 ± 2.9%) compared to saline (0.5 ± 0.6%). Topical administration (in situ) of 0.1 mL of OT (1.0 ng/mL) significantly reduced the IP (22.3.0 ± 0.6%) compared to saline (0.9 ± 0.7%). We also found by qPCR that the gene expression of oxytocin receptor is present in this tissue. Blockade of oxytocin receptors significantly attenuated the reduction in IP evoked by oxytocin i.v. or in situ. Therefore, the findings suggest that (1) intravenous oxytocin decreases IP due to bladder relaxation and (2) OT has local bladder effect, binding directly in receptors located in the bladder.

Highlights

The bladder dysfunctions cause social and mental discomfort and affect the well-being due to the difficulty of performing several normal activities in daily life
We observed no difference in the intravesical pressure (IP) and cardiovascular responses evoked by i.v. oxytocin comparing ovariectomized and sham rats
To the best of our knowledge, for the first time that intravenous administration of oxytocin decreases the IP in anesthetized rats

Summary

Introduction

The bladder dysfunctions cause social and mental discomfort and affect the well-being due to the difficulty of performing several normal activities in daily life. Dysfunctions of the lower urinary tract are frequent complaints, accounting for up to 40% in ambulatories of nephrology and urology (Bakker et al, 2002; Kajiwara et al, 2004; Hashim et al, 2009; Sureshkumar et al, 2009). The detrusor of the urinary bladder is composed of smooth muscle with gap junctions between its cells (Steers, 1998). The detrusor and the internal sphincter are innervated by the autonomic nervous system. Urine storage and micturition depend on coordination between two functional units: the urinary bladder and the striated musculature of the urethral sphincter (de Groat, 1998; Andersson and Hedlund, 2002)

Methods

Results

Conclusion